1. Field
The presently disclosed subject matter relates to a video projection system including multiple local video projection units, used as a pico projector, a head mount display (HMD) unit or a head up display (HUD) unit.
2. Description of the Related Art
Recently, a video projection unit is constructed by a two-dimensional optical deflector as an optical scanner manufactured by a micro electro mechanical system (MEMS) device manufactured using a semiconductor process and micro machine technology (see: JP2012-530264A & US2010/0315552A1). Since the MEMS optical scanner is focus-free, the video projection unit can be small in size.
On the other hand, a video projection system combining multiple video projection units for depicting one display image has been developed. This video projection system can be used as a multi-monitor display system or a projection mapping system for depicting display images on an outside wall of a building or the like.
A prior art video projection system such as the above-mentioned video projection system is constructed by a whole video projection unit and a local, video projection unit to carry out superimposed video projections (see: JP2004-70257A). In this case, the luminance of the superimposed image is adjusted to make the luminance of the combined whole image uniform.
In the above-described prior art video projection system; however, the whole video projection unit and the local video projection unit are assumed to have the same performance with respect to the luminance and the luminance resolution. Therefore, the larger the maximum luminance, the larger the luminance resolution. As a result, when the maximum luminance and projected area of the whole video projection unit are different from those of the local video projection unit, it would be difficult to project a display image with a high contrast and a wide dynamic range.